© Collin Grady from Las Vegas, Nevada.

Partial lunar eclipse

Dominic Ford, Editor
From the Eclipses feed

Time:       Altitude: °      Azimuth: °

A simulation of how the eclipse will appear from Ashburn.

The outer grey circle is the Earth's penumbra, and the inner black circle is the umbra. Any part of the Moon which passes within the black circle will be unilluminated, while any part within the grey circle will appear less bright than usual.




There will be a partial eclipse of the Moon, though it will be difficult to see from Ashburn since the Moon will rise partway through the eclipse, and only attain an altitude of 13° above the horizon by the time it ends.

The eclipse will last from 19:09 until 21:03, and maximum eclipse will occur at 20:06, when 25% of the Moon's disk will lie in shadow (all times given in Ashburn time).

Eclipses of the Moon are easy to watch with the unaided eye. A modest pair of binoculars will give a superb view of the Moon's surface, but are not required. Unlike solar eclipses, lunar eclipses are entirely safe to look at without the need to look through any kind of filter.

They occur whenever the Earth passes between the Moon and Sun, such that it obscures the Sun's light and casts a shadow onto the Moon's surface. The circular shadow cast by the Earth appears as a bite taken out of the Moon during its partial phases.

Sequence of events

The eclipse will begin at 17:37, when the Moon first enters a region of the Earth's shadow called the penumbra. In this outer part of the Earth's shadow, an observer on the Moon would see the Sun partially obscuring the Sun's disk, but not completely covering it. As a result the Moon's brightness will begin to dim, as it is less strongly illuminated by the Sun, but it remains illuminated.

At 19:09, the edge of the Moon's disk will enter the Earth's umbra. This is the region of space in which an observer on the Moon's surface would see the Earth completely obscuring the whole of the Sun's disk, and would find themselves suddenly thrust into darkness.

As an increasing fraction of the Moon's face creeps into the Earth's umbra, it will appear to have a growing bite taken out of it. We will see our planet's circular shadow sweep across the face of the Moon.

The table below lists the times when each part of the eclipse will begin and end.

Local
time
UTC
17:3722:37Moon begins to enter the Earth's penumbra
19:0900:09Moon begins to enters the Earth's umbra. Partial eclipse begins.
20:0601:06Greatest eclipse
21:0302:03Moon fully outside the Earth's umbra. Partial eclipse ends.
22:3503:35Moon leaves the Earth's penumbra
The geometry of a lunar eclipse
The geometry of a lunar eclipse. Within the penumbra, the Earth covers some fraction of the Sun's disk, but not all of it. In the umbra, the Earth covers the entirity of the Sun's disk. Any parts of the Moon's surface that lie within the Earth's umbra will appear unilluminated. Image courtesy of F. Sogumo.

Visibility of the eclipse

Eclipses of the Moon are visible anywhere where the Moon is above the horizon at the time. Since the geometry of lunar eclipses requires that the Moon is directly opposite the Sun in the sky, the Moon can be seen above the horizon anywhere where the Sun is beneath the horizon. The map below shows where the eclipse of July 17 will be visible.

Map of where the eclipse of July 2046 will be visible.
Map of where the eclipse of July 2046 will be visible. Click here to expand.

Further information

This eclipse is a member of Saros series 120. The exact position of the Moon at the moment of greatest eclipse is as follows:

Object Right Ascension Declination Constellation Angular Size
The Moon 19h48m -21°55' Sagittarius 30'24"

The coordinates above are given in J2000.0.

The sky on 17 August 2018
Sunrise
06:23
Sunset
20:01
Twilight ends
21:41
Twilight begins
04:44

6-day old moon
Waxing Crescent

42%

6 days old

Planets
Rise Culm. Set
Mercury 05:26 12:17 19:08
Venus 10:16 16:01 21:46
Moon 13:20 18:41 00:02
Mars 19:06 23:34 04:06
Jupiter 13:05 18:17 23:28
Saturn 16:51 21:35 02:23
All times shown in EDT.

Source

Espanak, F., & Meeus, J., Five Millennium Canon of Lunar Eclipses: -1999 to +3000, NASA Technical Publication TP-2009-214172 (2009)

You may embed the map above in your own website. It is licensed under the Creative Commons Attribution 3.0 Unported license, which allows you to copy and/or modify it, so long as you credit In-The-Sky.org.

You can download it from:
https://in-the-sky.org/news/eclipses/lunar_204607.png

Related news

17 Jul 2046, 19:57 EST  –  Full Moon
25 Jul 2046, 22:21 EST  –  Moon at Last Quarter
02 Aug 2046, 05:27 EST  –  New Moon
08 Aug 2046, 20:17 EST  –  Moon at First Quarter

Image credit

© Collin Grady from Las Vegas, Nevada.

Ashburn

Latitude:
Longitude:
Timezone:

39.04°N
77.49°W
EDT

Color scheme